_Barton beds._--Both in the cliffs of Headon Hill and Hordwell, already mentioned, the freshwater series rests on a mass of pure white sand without fossils, and this is seen in Barton Cliff to overlie a marine deposit, in which 209 species of testacea have been found. More than half of these are peculiar; and, according to Mr. Prestwich, only 11 of them common to the London Clay proper, being in the proportion of only 5 per cent. On the other hand, 70 of them agree with the _calcaire grossier_ shells. As this is the newest purely marine bed of the Eocene series known in England, we might have expected that some of its peculiar fossils would be found to agree with the upper Eocene strata described in the last chapter, and accordingly some identifications have been cited with testacea, both of the Berlin and Belgian strata. It is nearly a century since Brander published, in 1766, an account of the organic remains collected from these cliffs, and his excellent figures of the shells then deposited in the British Museum are justly admired by conchologists for their accuracy. _Bagshot Sands_ (2. _c_, Table, p. 197.).--These beds, consisting chiefly of siliceous sand, occupy extensive tracts round Bagshot, in Surrey, and in the New Forest, Hampshire. They succeed next in chronological order, and may be separated into three divisions, the upper and lower consisting of light yellow sands, and the central of dark green sands and brown clays, the whole reposing on the London clay proper.[199-A] Although the Bagshot beds are usually devoid of fossils, they contain marine shells in some places, among which _Venericardia planicosta_ (see fig. 171.) is abundant, with _Turritella sulcifera_ and _Nummulites laevigatus_. (See fig. 174. p. 200.) [Illustration: Fig. 171. _Venericardia planicosta_, Lamck. _Cardita planicosta_, Deshayes.]